The US aircraft carrier George Washington covers a wide area. Two weeks after joining in exercises in northeast Asia, off the Korean east coast, it was down in the South China Sea welcoming Vietnamese officials on board. The irony was incredible. US warplanes took off from aircraft carriers in the Vietnam war for missions culminating in the 'Christmas bombing' of Hanoi in December 1972 and the signing of the Paris peace agreement in January 1973. Nearly 40 years later, no one seemed intimidated by the proximity of this 88,000-tonne nuclear-powered monster off the Vietnamese coast.

And then, in another touch of irony, two days later, the US guided missile destroyer John McCain was in the central Vietnam port of Danang welcoming officials for 'cultural visits'. That's the same John McCain that shadowed a North Korean freighter off China's east coast for several weeks last year. Adding to the historical irony, the McCain is named for the grandfather and the father, both US navy admirals, of US Senator John McCain, imprisoned in Hanoi for more than five years after his navy plane was shot down in the war.

The blossoming relationship between the US and Vietnam is all the more remarkable considering Vietnam's relationship with neighbouring China, its strongest ally during the Vietnam war, and China's claims to sovereignty over the entire South China Sea. Now Vietnam appears to want to play one great power against another.

The confrontation exploded last month in Hanoi when Foreign Minister Yang Jiechi said US Secretary of State Hillary Rodham Clinton had staged 'virtually an attack on China' for calling sovereignty 'a leading diplomatic priority'. That exchange provided diplomatic background noise to Chinese air and naval exercises in the South China Sea around the Spratly Islands, a cluster of islets and reefs claimed in whole or part by Vietnam, the Philippines and Brunei as well as China.

While China was roiling waters near the islands, the George Washington was leading US and South Korean forces in northeast Asia in the wake of the sinking of the South Korean corvette, the Cheonan. China has protested at US plans to deploy the George Washington to the Yellow Sea.

The stand-off from southeast to northeast Asia raises the whole question of how to face the reality of China's rising power. Vietnam remains a communist country but ever since the 1980s has been turning to capitalism, as indeed has China. The issues between them are not ideological. The United States, once a military and ideological foe of Vietnamese communism, figures in the equation as a balancing force from which Vietnam can also profit as a trading partner.

The sense is that China is unnecessarily upset about these burgeoning ties. Clearly, memories of the Vietnam war are fading. Now East Asian nations worry about China's claims over waters where US warships provide a reminder of the dynamics of shifting power relationships.

Donald Kirk, based in Seoul and Washington, covered the Vietnam war for newspapers and magazines, and has written two books about it